Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: literarymadness on Sunday,June 07, 2020, 02:01:59 AM
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Every since I read about them in the Miles Wilkins' book and saw them in photos on a couple this forum's member's cars, I have been wanting a Euro TC Stromberg Intake Manifold set-up. A UK transplant in France (on the lotuselan.net forum) had the pair minus the balance tube and I bought them the day they went up for sale. They finally are on my car and I took some photos of the set-up before the Air box gets put back on.
Lotus only made them for 18 months and made two types: the early Mid-Level Balance Tube version and the later superior High-Level Balance Tube version. Some of them actually were put on by the factory on some ROW (Q vin code) Europa TCs. But Lotus felt they were making too much power for the 336 transmission. But most were put on Elans. For the record, according to the Miles Wilkins' book, the fastest Elans ever tested had Stromberg heads (high compression with Sprint Cams) and not Webers. They were only within three horsepower of the Weber and they had more torque.
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Thanks for posting the pics Literary!
Have you driven it yet and noticed a difference in how it runs?
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Just wondering, are the hoes on the top of the manifolds covered by plugs or are part of the casting.
When I had my high balance tube manifolds made, my machinist had a hell of a time trying to figure out how to drill out the holes for the balance tubes. It takes a special right angle tube to make the hole which he did not have. He decided to finally come in from the bottom to make the hole and drill/tap threads for a plug to cover the hole. In my opinion these manifolds make for a much cleaner looking engine bay especially with tubular headers.
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@Joji: Rather than guessing, I will give them a close examination when I go back to the shop and get back to you. Where did you mount the throttle cable? Your machinist did an incredible job by the way. They look fantastic. Could you post a couple of more photos of yours, if you wouldn't mind. I found a couple of other shots of some other Euro TC intakes online and posted them below.
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I agree with Joji! Yours look great!
It looks like your builder used Thackery washers under you Strombergs but the nuts are tightened. The manual calls for an 'O' ring sealing the carbs to the manifold and a 0.070 gap between the "adapter flange" and the carburetor. This is similar to how Weber DCOEs are mounted only the Thackery washers are supposed to be tightened such that there is a 0.035" - 0.050" gap between the coils.(I would note that I have seen some Weber DCOEs mounted rigidly to their manifolds.) I was wondering if your builder had tightened them all the way down for a reason.
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I agree with Joji! Yours look great!
It looks like your builder used Thackery washers under you Strombergs but the nuts are tightened. The manual calls for an 'O' ring sealing the carbs to the manifold and a 0.070 gap between the "adapter flange" and the carburetor. This is similar to how Weber DCOEs are mounted only the Thackery washers are supposed to be tightened such that there is a 0.035" - 0.050" gap between the coils.(I would note that I have seen some Weber DCOEs mounted rigidly to their manifolds.) I was wondering if your builder had tightened them all the way down for a reason.
I remember reading about "Thackery washers" a while back and never gave it another thought, but this thread made me take a look at my setup and it appears somewhere along the line my Strombergs were rigidly mounted. I've been driving in blissful ignorance that I had "frothing" in my float chambers (the supposed problem soft mounting is supposed to overcome). What are the symptoms of said frothing, and should I immediately invest in new o-rings and Thack-washers? Incidentally, it looks like the studs on my manifold aren't long enough for 0.050" o-ring gap and the "Thacks".
Tom
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@BDA: There are Triumph Stromberg gaskets between the head and the intake and there are O-rings between the carbs and the Adapter plates. The spring washers are tightened within the tolerances. Thanks for the close look.
@Surfguitar: Is there any reason you mounted the throttle cable from the top rather rather than using the hole that is through middle of the intake?
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I didn't mean to alarm anyone! That's why I included that story about people solidly mounting their DCOEs. I think if you were having frothing problems you would be running lean and you'd probably have some spitting and popping from your carbs. If it runs good, you should be fine. As you say, unless you get longer studs, you don't have room on your studs to install Thackery washers (or their rubber equivalent) anyway.
If you're really curious about it, if you know who set them up, you could ask him about it or you can talk to Ray at r.d. enterprises or Ken at Dave Bean.
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I hadn't heard of anyone complaining of fuel frothing with Strombergs before over the years. I have no idea what the symptoms of fuel frothing might be. I'm suspecting it would be similar to fuel boil of the float bowl that my Weber on my S2 experiences from heat soak, stumbling under power until fuel starts flowing. If you haven't experienced any symptoms so far, I would hold off installing the Thackery washers until you have to remove the carbs for another reason. The only other problem I can see is vibrating parts off the carbs.
My throttle cable attachment is similar to what you have, a bracket between the two manifolds. I've attached a few photos of other versions of HBT manifolds I've found on the web.
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@Surfguitar: Is there any reason you mounted the throttle cable from the top rather rather than using the hole that is through middle of the intake?
Just another mystery from my deceased PO.
t
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@Joji: That bracket really looks great. It looks a lot less obtrusive than mine. Did you machine that yourself? I also actually love the red anodized version. Here are the intakes before they were shipped from France and refurbished here by Steve Smith (Twin Cam Racing).
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Looking at the Fed-spec intake from both sides, the plumbing looks like a disaster and excessive. Now granted it was designed to reduce emissions. But you can see that all that extra plumbing did less balancing of the air flow between the two carbs and robbed power. The engineers at the time admitted it was a rush job and they wished they had enough time make the design more efficient.
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Fuel frothing is a high rpm issue that rears its head with prolonged flat out driving. It's not an issue in normal city and highway driving. So, if you have mounted your carbs too rigidly, you may not notice anything until you take it to the track or climb a long steep mountain pass. Given both Lotus and Renault engineered flex into their dual side draft carb intakes, I would make keep it!
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Here is my throttle cable bracket. In fear of the side wear on a throttle cable I utilized small ball bearings on each end of a tube between the head stud holes. Bearings are from a RC car wheel bearings, which are really small. The tube rotates as the cable moves up/down on the throttle shafts. So far its worked now for 20 years.....
Jerry Rude
4005R
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@Jerry: Very cool solution and you were able to maintain an angle similar to the original Cam Cover cable bracket. :beerchug:
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It looks like one could approximate the euro-spec manifold with some careful bandsaw surgery on the fed-spec manifold. The outlet ports could be machined to accept a balance pipe and the returns could be plugged. (or maybe I have that backwards.) Anybody want to sell or donate their unused old manifold for an experiment?
Tom
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Here's mine a few years ago.
http://www.lotuseuropa.org/LotusForum/index.php?action=dlattach;topic=464.0;attach=1924 uhh
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My car came with the Hitachi SU carbs bolted directly to the cylinder head when I bought it in 1986. There was no balance manifold. Since I thought it should have a balance tube, I did the following when I rebuilt the head in 1989.
I took a long 1/2" drill bit and drilled through the rear cylinder head manifold vacuum boss and went through both sides of the rear carb manifold and 1/2 through the front carb manifold.
I then took a 1/2" od tube and devcon epoxied the tube between the front and rear carb manifold. I then blended the tube ends to the Id of the front and rear manifolds. Finally I threaded the rear vacuum port to 3/8 pt.
It has been in since 1989 and the devcon never cracked and leaked. I learned at Chrysler that Devcon worked really well for customizing cylinder heads.
I attached some photos. What this design does is reduce weight by removing the
balance tube manifold and it allow more room for a larger airbox and velocity stacks.
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For some reason, the first picture won't display and gives an error when you click on file name! :(
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I will try to repost
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That fixed it!
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My car came with the Hitachi SU carbs bolted directly to the cylinder head when I bought it in 1986. There was no balance manifold. Since I thought it should have a balance tube, I did the following when I rebuilt the head in 1989.
I took a long 1/2" drill bit and drilled through the rear cylinder head manifold vacuum boss and went through both sides of the rear carb manifold and 1/2 through the front carb manifold.
I then took a 1/2" od tube and devcon epoxied the tube between the front and rear carb manifold. I then blended the tube ends to the Id of the front and rear manifolds. Finally I threaded the rear vacuum port to 3/8 pt.
It has been in since 1989 and the devcon never cracked and leaked. I learned at Chrysler that Devcon worked really well for customizing cylinder heads.
I attached some photos. What this design does is reduce weight by removing the
balance tube manifold and it allow more room for a larger airbox and velocity stacks.
Nice shiny porting on your intake! Are your SU carbs soft mounted with Thackery washers and o-rings, or has the frothy float chamber thing not been an issue?
t
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No frothing. Hitachi SU's and early british SU's have the float bowels mounted in rubber.
I was thinking though. Why don't American carbs have the frothing?
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Fuel frothing is an engine balance/design/tuning issue. V8s are inherently better balanced than a 4 cylinder. 4 cylinder engines have balance issues that can only be solved by the addition of balance shafts. As auto engines are rubber mounted, balance shafts are seldom fitted unlike in modern motorcycles.
Tuning is a factor as well as fuel frothing is an issue with high rpms. The most well known example of this is the MGA twin cam. The push-rod engine didn't rev as high and had no problem with frothing. Unfortunately MG didn't figure out what the issue was until after the engine production was cancelled. Had they, the MGB, and MG itself, might have had a completely different history. Now MGA twin cams have flexibly mounted carbs and no issues.